Stihl fs 100 rx trouble

[Isaac]

I have a stihl 100 rx that is running real sluggish It doesn't run rough , just slow. No matter how much line you have out or zero for that matter. It still runs like it is under a load. Not much happens when you turn the adjustment screws on the carb, if anything it gets worse. Thought it might be the muffler. Got rid of the screen a long time ago and there isn't any oily splooge coming from it. I've tried echo red armor pre-mixed gas,VP pre-mixed, and also 100 octane race gas mixed with Maxima k2 at 40:1. Nothing seems to make much of a difference. Any help would be appreciated. Thanks

 

[czar800]

How's the air filter?

 

[T.Roller]

Check air filter. Also some of those trimmers had coil issues that would also cause that. I'd q lso look at carb

 

[Isaac]

The air filter is clean. I pulled then muffler today and found quite a bit of carbon on the exhaust valve. Also pulled the plug and the top of the piston is pretty nasty. Haven't bothered the carb. Confused why I have so much carbon because I always use quality fuel and oil. Dont know much about a 4 mix but guess I'm going to tear into it this weekend. Any ins and outs I need to know about a 4 mix? Valve adjustments etc?

 

[treesmith]

The valves probably need doing, i have the right shim but can't remember the size, I was told to change the gasket at the same time

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[backhoelover]

sound like you cam is wore down

 

[Isaac]

Thanks for the help guys. Is it worth tearing in to? Or should I call it scrap? In the past I've had them worked on by dealers. It seems like once these trimmers start acting up you can't get them running like new again. I hate to spend a bunch of money on a 6 year old trimmer when a new one is $350.
Treesmith, What gasket are you referring to?
Backhoelover, Is cam wear a common problem? Also how much of a pain is it to change?

 

[Time's Standing Stihl]

I have an fs90 that I had issues with last week. Moved to the country 3 yrs ago and haven't had the need to use it. So I decided to to a muffler mod on it and trim the limiters on the carb. Had a heck of a time setting the carb. All over the place. Come to find out, my 4 mix doesn't like 32:1. Threw some VP 50:1 and it tuned right in. Carb was still super super touchy.

Could be your valves need adjusted?

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[Isaac]

I have an fs90 that I had issues with last week. Moved to the country 3 yrs ago and haven't had the need to use it. So I decided to to a muffler mod on it and trim the limiters on the carb. Had a heck of a time setting the carb. All over the place. Come to find out, my 4 mix doesn't like 32:1. Threw some VP 50:1 and it tuned right in. Carb was still super super touchy.

Could be your valves need adjusted?

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The trimmer only reacts at the very last point of adjustment, on the lean side, i think. How did you do your muffler mod? I think the excess of carbon on the valves and piston may have come from a stuffy muffler.

 

[Time's Standing Stihl]

Ain't nothing fancy, but it works. ...the top comes straight out of the exhaust port. The muff is baffled throughout, so I drilled a couple lower by the original port.

 

[treesmith]

Treesmith, What gasket are you referring to?

Don't know the trimmer you have but on the 4mix engines at work the valves are under a pressed tin cover with a square cork gasket, I was told to change this gasket every time the valve clearances were done which should be often, can't remember the figure but it was something like every 40hrs or less

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[Isaac]

Don't know the trimmer you have but on the 4mix engines at work the valves are under a pressed tin cover with a square cork gasket, I was told to change this gasket every time the valve clearances were done which should be often, can't remember the figure but it was something like every 40hrs or less

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Thanks for the tip. I had no idea the valves had to be done that often. I'm sure the that might have something to do with the problem.

 

[Isaac]

Ain't nothing fancy, but it works. ...the top comes straight out of the exhaust port. The muff is baffled throughout, so I drilled a couple lower by the original port.

Thanks I'll give it a whirl.